The movement of heavy crude through pipelines is difficult. The pumping of heavy crude, fuel oil, and the like is difficult because of the high viscosity of these materials and their resulting low mobility. A known method in the prior art for transporting these heavy, viscous crudes is the addition of lighter hydrocarbons, etc. to the heavy, viscous crudes by a technique such as distillate blending. This technique is expensive as it requires the addition of expensive, light crudes to transport the heavy, less valuable crude. Also, light crudes are more difficult to obtain than the heavy crudes.
Another known method for the transport of heavy, viscous crude is by heating the crude at frequent intervals along the pipeline. This method requires expensive heating equipment to be installed along the pipeline, and also requires maintenance of this equipment. This method also results in a loss of production that can amount to 15% or more of the crude being transferred, the loss resulting from the crude or other energy source utilized to heat the crude.
Yet another method involves the pumping of viscous hydrocarbon through a pipeline surrounded by a lighter viscosity liquid, such as water. In such cases the pressure drop through the pipeline is substantially that of the lighter viscosity liquid. This method of transportation has several disadvantages, however. The major disadvantage is the loss in core flow stability while being pumped over long distances. Slope changes, pipeline diameter changes, transport through booster or repumping stations, and the like expedients are all detrimental to stability. Also, if flow ceases for any reason, the fluid becomes very difficult to pump when transport is resumed, as the core intermixes with the outer layer once the flow of the fluid is ceased or otherwise interrupted.
The use of emulsions to transport heavy crude is also known in the art. Emulsions are typically prepared by adding a mixture of surfactant, blend of surfactants, stabilizer, corrosion inhibitor, pour point depressor and alkaline or neutral pH water to the heavy crude. However, these prior art emulsions fail to optimally reduce viscosity and improve stability of the emulsion while the emulsion is being transported through the pipeline.
Also, conventional systems prepare the heavy crude oil emulsion by conventional mixing using static or dynamic mixers in addition to other preparation steps. At various stages in such a conventional system, as the emulsion is prepared, the emulsion is first mixed and then pours out of pipes directly into tanks. U.S. Pat. No. 5,000,872 to Olah illustrates such a conventional system in which, for example, the emulsion travels through a static mixer just before pouring into a final emulsion tank at the entry to the transport pipeline. In such a system an opportunity for producing droplets of a uniform size without the need for additional mixers is lost.
Heavy crude emulsions, as well as methods of making such emulsions are disclosed in U.S. Pat. No. 4,618,348 to Hayes et al.; U.S. Pat. No. 4,781,207 to Balzer et al.; U.S. Pat. No. 4,265,264 to Sifferman; and European Patent No. 0 156 486 A2 to Chirinos et al. The emulsifiers utilized in the prior art are numerous. The emulsions in the prior art are manufactured using a variety of mixing conditions and techniques. However, the emulsions of the prior art are difficult to break down into water and oil. Furthermore, the emulsions of the prior art have not been optimized for viscosity and stability to effect efficient transport of these emulsions through pipelines and ultimate utilization.
It has now been found that certain combinations of anionic, nonionic and/or amphoteric emulsifiers, optionally in combination with natural and/or synthetic stabilizers, such as gum, gelatins, carboxymethylcellulose, and the like, when blended at certain shear rates with heavy crude, fuel oil, or the product bottoms from oil barrels, provide an improvement over prior art emulsions. Preparing the emulsions under optimum mixing conditions further enhances their properties. The resulting emulsions form reduced viscosity fluids of controlled stability which fluids can be transported with less effort and which can be utilized more efficiently at the desired destination.
In addition, according to this invention, a diffuser is attached to the end of pipes through which the emulsion must flow to enter an emulsion tank. As the output of the diffuser sprays into the tank droplets of a more uniform and, if desired smaller, size than produced by conventional systems are formed.